In LTE, in particular in LTE Advanced, carrier aggregation (CA) has been specified in Rel-10. Carrier aggregation allows increasing the transmission/reception bandwidth by aggregating component carriers. In order to use carrier aggregation, an eNodeB (eNB or base station) first needs to configure a user equipment (UE) with one or more secondary cell(s) (SCell(s)) by RRC (radio resource control) signaling and then activate the SCell(s) by MAC (medium access control) signaling. The eNode B can also deactivate the SCell(s) by MAC signaling if it decides that CA is not needed anymore. The RRC configuration may be reliably acknowledged by higher layer signaling; however, the MAC activation/deactivation of the SCell is acknowledged by a L1 ACK/NACK. In case there is an NACK-to-ACK or DTX-to-ACK (false alarm) error, the eNode B and the UE will not be synchronized (in-sync) with respect to the SCell's activation status. The following problems may arise as a result. The eNode B may assume that the SCell is active while it is deactivated at the UE. This may lead to the scenario that any PDCCH/PDSCH and PUSCH scheduled transmissions on the SCell will be erroneous and will cause unnecessary interference. The eNode B may assume that the SCell is not active while it is activated at the UE. This may lead to the scenario that the UE will send CSI transmission which are not expected and will cause interference or that the UE will unnecessarily monitor the PDCCH on SCell and will waste its battery.
There may be a need for an improved system and method being adapted to reduce the probability of false activation or deactivation of a secondary cell or communication carrier.